In recent years, significant developments have been made in high-energy chemical lasers.
In addition to the non-consumable laser hardware itself, advances have been made in consumable sub-system technology. A fieldable, high-energy chemical laser device requires a disposable oxidizer, fuel, and pumping systems so that logistics do not become unmanageable. The chemical pump has advanced through practical demonstration tests, and solid oxidizers have already been demonstrated. The chemical pump is based on an activated calcium material, isostatically pressed as internally tapered angular discs, which react with the laser effluent, producing non-volatile products. Solid oxidizer work has focused on NF.sub.4 salt technology and has resulted in the development of the NF.sub.4 BF.sub.4 combustor. Formulations of NF.sub.4 BF.sub.4, when combusted, yield 30% weight-by-weight NF.sub.3 +F.sub.2 laser reactants and a solid residue.
High-energy chemical lasers require hydrogen and/or deuterium as pre-combustor and cavity fuels. Although available from high-pressure gaseous supply systems, they present severe logistic and safety problems. Solid fuel generators, for the production of hydrogen and/or deuterium, are needed.
Hydrogen generators employing mixtures of lithium aluminum hydride and ammonium chloride have been proposed. Although the formulations provide pure hydrogen, the residue undesirably contains lithium hydride, an active species. Mixtures of sodium tetrahydroborate and iron oxide have also been proposed. Although producing pure hydrogen and an inert residue, hydrogen yield is only about 2.8% weight-by-weight, which is insufficient for practical application.
Compositions based on ammonium salt-sodium tetraborate have also been developed, but have been found to produce significant quantities of ammonia, a laser deactivator, and exhibit a maximum yield of 5.5% weight-by-weight hydrogen.
In U.S. Pat. No. 4,157,927, incorporated herein by reference, in which one of us is a named inventor, there is disclosed the use of amine-boranes and their derivatives as solid propellants to generate hydrogen or deuterium upon combustion. It is disclosed that functional compositions can be formulated by blending amine-borane or its derivatives with heat-producing compounds, such as LiAlH.sub.4, or a mixture such as NaBH.sub.4 /Fe.sub.2 O.sub.3. It was proposed that the resulting mixture be pressed into pellets and ignited to produce hydrogen (or deuterium if the analagous per-deutero reactants are substituted for the hydride ones specified), and by-products that are non-deactivating diluents. It was found, however, that when, as discussed in the patent, ammonia-borane was combined with NaBH.sub.4 /Fe.sub.2 O.sub.3, intimately mixed and pressed into a pellet, a strong odor was detected emanating from the pellet, indicating that the pellet was thermally unstable at ambient temperature.